You should move that pushable object approximately in the middle between two crawlspaces, so when you raise the gray block (it's timed) you can use it to jump from one crawlspace to the other and get the key.

Btw that's a well-known bug when there is an object on the pedestal. You can pick it up from any height as long as you are on the same vertical space.

A man who introduced me to Lara back in 1996, more than a friend, my second father....
Dusan "Dule" Petrovic (1965-2018)